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Open AccessArticle

Aquaporins Respond to Chilling in the Phloem by Altering Protein and mRNA Expression

by Ryan Stanfield 1,* and Joan Laur 2
1
Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2R3, Canada
2
Institut de Recherche en Biologie Végétale, Université de Montréal, Montréal, QC H3T 1J4, Canada
*
Author to whom correspondence should be addressed.
Cells 2019, 8(3), 202; https://doi.org/10.3390/cells8030202
Received: 31 January 2019 / Revised: 19 February 2019 / Accepted: 21 February 2019 / Published: 27 February 2019
(This article belongs to the Special Issue Aquaporins)
Previous experiments using heat exchangers (liquid cooled blocks) to chill a portion of plant stem have shown a transient stoppage in phloem translocation and an increase in measured phloem pressure. Although a chilled-induced stoppage of phloem transport has been known for over 100 years, the mechanism of this phenomenon is still poorly understood. Recently, work has highlighted that aquaporins occur within the plasma membrane of the sieve tubes along the entire source-to-sink pathway, and that isoforms of these water channel proteins may change dynamically. Aquaporins show regulatory roles in controlling tissue and cellular water status in response to environmental hardships. Thus, we tested if protein localization and mRNA transcript abundance changes occur in response to chilling in balsam poplar (Populus balsamifera) using immunohistochemistry and qrtPCR. The results of the immunolocalization experiments show that the labeling intensity of the sieve elements treated for only 2 min of chill time significantly increased for PIP2. After 10 min of chilling, this signal declined significantly to lower than that of the pre-chilled sieve elements. Overall, the abundance of mRNA transcript increased for the tested PIP2s following cold application. We discuss the implication that aquaporins are responsible for the alleviation of sieve tube pressure and the resumption of flow following a cold-induced blockage event. View Full-Text
Keywords: phloem transport; cold-induced inhibition; aquaporins; PIP1; PIP2; sieve tubes; qrtPCR; immunohistochemistry phloem transport; cold-induced inhibition; aquaporins; PIP1; PIP2; sieve tubes; qrtPCR; immunohistochemistry
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MDPI and ACS Style

Stanfield, R.; Laur, J. Aquaporins Respond to Chilling in the Phloem by Altering Protein and mRNA Expression. Cells 2019, 8, 202.

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